The present invention relates to devices for deforming and ejecting a deformable intraocular lens for insertion into a small incision in an eye, the device comprising a) a housing, b) a lens transporting duct in a front part of the housing defining a duct axis, the duct having a front end with a cross-section adapted to the lens in deformed state with small maximum dimensions transversal to the duct axis, a rear lens-receiving end with a cross-section adapted for the lens in un-deformed state, or less deformed state, than at the front end, with larger maximum dimensions lateral to the duct axis than at the front end and an intermediate convergent duct part between the front and rear ends with a varying cross-section shape, having decreasing maximum dimensions lateral to the duct axis when moving from rear to front in the duct and c) a plunger operative to displace the lens in the duct at least in the forward direction. The invention also relates to methods corresponding to the operational steps of the devices.
Deformable intraocular lenses are used both for replacement of the natural lens in cataract afflicted eyes and for surgical implantation of an additional lens for refraction correction purposes. In a typical cataract operation the eye ball is punctured close to the limbus and an instrument is inserted and used to disintegrate and remove the opaque eye lens. Next an artificial lens is inserted through the incision to replace the natural lens and is kept in place, normally in the posterior chamber, by haptics in the form of either flexible wings (one piece lens) or flexible spiraling legs (two or more piece lenses) later developed for better stabilization in the eye. Healon (R) or a similar agent is introduced during both steps in order both provide bulk and protect sensitive tissue during the operation. The procedure is about the same for phakic corrective lenses although the natural lens is normally not removed and the thinner lenses can be located also in the anterior chamber in front of the iris.
The eye incision size necessary is determined by the lens size and the first generation of hard lenses, typically made from PMMA, required a cut corresponding to the lens diameter.
Soft lenses have been developed for the purpose of limiting the incision needed to insert the lens in the eye, thereby reducing the risks for eye ball distortions and infections and improving post-operative healing. The soft lens, e.g. made from silicone, can be folded or rolled to a fraction of its initial diameter and then regains its original shape within the eye. Yet, manual folding followed by insertion, release and manipulation of the lens through the minimal incision requires the physician to execute high skill and various tools have been developed and marketed to facilitate these steps. Typical general problems include the establishment and maintenance, without tearing, of the small incision not to introduce deformation and subsequent astigmatism, not to touch the cornea or the thin endothelial cell layer, to control the positioning of both lens optic part and especially the flying haptics and to avoid any infection or introduction of debris into the eye.
Although the deformable lenses have solved a lot of problems, other are introduced instead. The lens material is softer and more susceptible to damage, cutting or shear by hard or sharp parts or imperfections in implanters or other manipulating devices, problems exaggerated by the material friction making the material easily caught in tolerances necessarily present between device parts. Also the lens haptic parts need consideration. The lens has to be folded or deformed so as to avoid collision or overlap between the haptics and their anchoring points in particular, yet not so far separated that a plunger attacks directly thereon. It has to be folded not to be damaged during transport and to be released and unfolded properly at exit. Most lenses are asymmetrical with a distal and a proximal side and need to be ejected in proper oriented in the eye. Yet the very necessity that the haptics are the most peripheral lens parts makes them especially exposed and, furthermore, force applied thereto give high torque and twisting moment to the lens, easily resulting in misalignment or rotation of the whole lens, in turn resulting in improper folding or deformation, damage to haptics or optics and improper release at exit, all most often manifested in abnormally high displacement resistance.
These soft lens characteristics puts severe demands on any device for their manipulation and implanters with lens transportation channels in particular. The overall demand on such a channel is that it should be smooth not to impose shear, friction, grinding, cutting or pinch to the lens optic or haptic and this applies both to any transition in monolithic channel parts and to joints in multiple part channels, the latter to be avoided as far as possible as grades and misalignments are almost inevitable unless instead the parts are fused, polished and finally cleaned to avoid any trace of debris. Yet multiple parts may be unavoidable, e.g. when providing for doors or closures to allow lens insertion or when using cartridge type inserts for lenses deformed by separate or external means. In general the lens transport through the channel comprises at least two distinct phases. In a first phase the lens is transported, possibly under complete or partial deformation, to a stand-by position, ready for release, close to the end of an elongated tip designed for insertion through the incision into the eye, although this phase is commonly performed before the tip has been inserted into the eye. In a second phase, performed with the tip inserted into the eye, the lens is pushed the remaining short distance out from the stand-by position for released in the eye. A plunger arrangement need to cope with the different requirements in these phases, the first in general needing a slow but steady force and speed not to stress the lens whereas the second is more of a short triggering action as the lens tend to unfold automatically at the end tip due to its stored elastic energy. The force variations are considerably more pronounced in the first phase if a lens deformation takes place, increasing until completion of deformation and then dropping, and in the second phase if the tip is designed with deformation features or release features, e.g. slits. In manual operation force drops may easily result in inadvertent displacements, especially disastrous at final release. Lens deforming convergent channels poses additional problems, e.g. in respect of controlled initiation as well as continued folding, especially in view of the haptic problems outlined. The problems tend to be more pronounced for the two or more piece lenses with their delicate and elusive spiralling haptics compared to the more sturdy and localized single piece haptics.
Although many tool types have been proposed it is believed that no suggestion meets the abovesaid requirements to any acceptable extent. Early device suggestions were merely auxiliary fixtures or jigs for assisting forceps or hook handling of the lenses, as exemplified by U.S. Pat. Nos. 4,702,244, 5,100,410 and 5,176,686 but neither high deformation degrees nor small incisions could be obtained or acceptable manipulation control. Many later proposals rely on separate means for lens deformation and lens transportation respectively, e.g. jaws, paddles, e.g. U.S. Pat. No. 4,880,000, or deformation members acting lateral to the channel. Such devices necessarily comprises several parts between which the lens is deformed, and the lens deformed between such parts is often inserted as a cartridge into a reusable implanter device, all parts tending to introduce the potentially harmful imperfections described. Moreover, such devices rely on operator skill, rather than assistance by convenient device safety features, for correct lens insertion and manual deformation, easily resulting in arbitrary and inconsistent folding and release behavior. As a typical example the U.S. Pat. Nos. 5,494,484 and 5,800,442 relate to a device for lens deformation between two hinged half tube, wherein skill is required not to invoke random results or pinching of optic or haptic. Although the already deformed lens should allow for a simple plunger advancement mechanism a screw arrangement is used, requiring an impractical two hand operation in the critical moment of lens release. Numerous proposals have also been made for devices with convergent channels in which the lens is folded and deformed during forward transport in the channel before final release at the end. The lens may be inserted flat or slightly bent at the channel entrance for further downstream deformation, proper folding frequently assisted by grooves or other structures in the convergent channel parts. Typical examples are disclosed in U.S. Pat. Nos. 4,919,130, 5,275,604, 5,474,562, 5,499,987, 5,584,304, 5,728,102, 5,873,879 (WO96/03924), DE 3610925, WO 96/20662 and WO 96/25101. Although such deformation devices may require less operator skill the results are far from satisfactory and consistent. As said, the transport deformation principle requires high and varying transportation forces, increasing stress and possible damage of the lens from channel and plunger. A further cause of lens damage is the fact that such devices have a larger entrance than exit channel cross-section, the added area sometimes added to facilitate insertion of the unstressed lens but always needed to accommodate the plunger cross-section area in the height direction. Shear between channel and plunger is then unavoidable where the cross-section decreases or changes, often causing squeezing or even cutting of the soft lens material in addition to the potentially destructive point force applied between the plunger and the non-deformed lens. Also the initially unfolded lens is highly susceptible to misalignment due to the twisting forces described, often resulting in improper folding and later unfolding or damage to the displaced optic or haptic, in spite of extensive means proposed to accommodate and protect the haptic during lens pushing. Also the problem of convenient use of the device in view of the strongly varying force requirements remains unsolved as well as the risk for actual implantation of a damaged lens due to the masking effect of uncontrolled force variations.
A main object of the present invention is to avoid the problems with hitherto used and proposed devices for folding or deforming and later ejecting soft intraocular lenses. More specifically, an object is to offer a device with reduced risks for lens damage. Another object is to offer a device convenient to use and with operation characteristics adapted to each implantation phase. Still another object is to provide a device preventing improper use or operation steps. Yet another object is to provide a device preventing implantation of damaged lenses. A further object is to offer a device with reduced risks for damage of the lens and with reduced lens stress. Another object is to avoid lens damage due to device imperfections and tolerances. Still another object is to avoid damage in connection with lens deformation based on transport in convergent channels. Yet another object is to secure proper lens folding, transport and release with respect to both lens optic and haptic parts. A further object is to prevent lens dislocations and lens rotations relative to the desired movement pattern. Another object is to provide a device useful for either a lens with single or multiple part haptics. A further object is to provide a device simple and inexpensive and possible to use as a disposable or single-use device.
These objects area reached with the characteristics set forth in the appended patent claims.
By use of a plunger arrangement including a track and follower arrangement requiring a rotational, screw-threaded, movement under a first part of the plunger forward movement and allowing or requiring a more axial, pushing, movement during a last part of the lens transportation several convenience and safety objects are reached. The initial threaded movement secures high force and slow speed in the sensitive initial parts of the lens movements, possibly including plunger contact with the lens including haptic accommodation, transfer from a loading cassette to an implantation tip, at least some deformation of the lens, in connection with convergent channel deformation orientation and substantial deformation under highly variable force requirements, and precise positioning of the lens in a release position close to the device tip. The operation is preferably made as a preparative phase prior to contact with the eye and encourages use of a two-hand grip and close monitoring of proper lens transport and final lens positioning in the device and any inadvertent lens ejection is prevented by the requirement for rotation movements. During the implantation phase the device tip should be positioned within the eye and only a short final forward movement of the plunger should be needed to eject the lens from the release position. The now allowed or required pushing movement allows a delicate forward final movement of the plunger, which can be made with a single hand grip, equal for left and right handed people, and does not require a cumbersome two-hand grip prone to induce tilting and rocking in the sensitive eye incision and freeing the operators other hand for other necessary actions. Further safety is obtained if the transition between the phases is compulsory e.g. with a definite stop for the screw-threaded rotation movement at the precise spot for lens release at the tip and rotation prevention for the plunger actuator during the last plunger displacement. In connection with arrangements for lens deformation by transportation in a convergent channel with along the channel varying width to height ratio in the cross-section, as known per se, several advantages are obtained if a plunger front is used which can be reshaped to adapt to the changing ratio. A larger contact area between plunger tip and lens can be utilized than with a plunger tip of constant shape, giving less surface pressure and correspondingly less risk for lens damage. Furthermore, the difference is largest where needed, namely in the early deformation phases when high and varying forces are present. The force is applied more optimal with pressure also along channel periphery and not only centrally, improving transport and reducing lens dragging and deformation. With a re-shapeable and channel following plunger the channel design can be adapted purely for the lens folding purposes, improving control over this process. There is no longer any need for additional channel area for plunger parts not affecting the lens in the early stages, allowing reduced or eliminated such area, giving less overall friction, facilitated design with fewer parts and better part divisions, fewer edges or discontinuities and smoother surfaces, highly compatible for disposable purposes. Above all, with such a design the deformed lens cannot expand into such additional areas, strongly reducing the risks for squeezing, pinching and cutting the lens between plunger and channel. The advantage is most pronounced if or where the channel has roughly constant cross-section area, in spite of its continuous shape variation, and mostly so if the cross-section at each channel point corresponds to the cross-section of the lens. The optimal use of the plunger front area all over the channel length easily allows for the arrangement of free areas for any type haptic accommodation and protection. A fixture or jig, preferentially gripping on a haptic part, can be used to secure the lens in its initial undeformed state, thereby preventing improper positioning, reducing the requirements for skill, preventing rotation or twisting of the lens and generally securing the intended folding pattern.
Further objects and advantages with the invention will be evident from the detailed description hereinbelow.
In the absence of explicit statements to the contrary, as used herein expressions like xe2x80x9ccomprisingxe2x80x9d, xe2x80x9cincludingxe2x80x9d, xe2x80x9chavingxe2x80x9d, xe2x80x9cwithxe2x80x9d and similar terminology shall not be understood to be exclusively restricted to recited element but shall be understood to allow for the presence of further elements as well and shall be understood to cover any element in integral, subdivided or aggregate forms. Similarly, expressions like xe2x80x9cconnectedxe2x80x9d, xe2x80x9cattachedxe2x80x9d, xe2x80x9carrangedxe2x80x9d, xe2x80x9cappliedxe2x80x9d, xe2x80x9cbetweenxe2x80x9d and similar terminology shall not be understood to cover exclusively direct contact between the recited elements but shall be understood to allow for the presence of one or several intervening elements or structures. The same applies for similar expressions when used for description of forces and actions.
Also as used herein, positional and directional statements for device, such as xe2x80x9caxialxe2x80x9d, xe2x80x9cfrontxe2x80x9d and xe2x80x9crearxe2x80x9d and xe2x80x9cforwardxe2x80x9d and xe2x80x9crearwardxe2x80x9d, shall be understood with reference to the lens delivery direction. The device xe2x80x9caxialxe2x80x9d direction shall be understood as a line centered in the lens duct, although such an axis need not always be entirely straight but can be curved, e.g. in convergent type ducts where the duct may have a varying cross-section shape.
A soft lens may be given a reduced diameter, suited for insertion in a small eye incision, in a number of different ways, known per se, e.g. rolled to spiral form, single or multiple folded to various forms of single or multiple overlap or bellow shape, radially deformed or stretched under axial expansion or elongation etc. and in reality any method used normally will involve several pure size reduction principles. As used herein, expressions like xe2x80x9cfoldingxe2x80x9d, xe2x80x9cbendingxe2x80x9d, xe2x80x9cdeformingxe2x80x9d, xe2x80x9ccompressingxe2x80x9d, xe2x80x9cstressingxe2x80x9detc. are used interchangeably to indicate any kind of size reduction method for implantation purposes and shall not be understood to be limited to any particular method, unless otherwise specifically indicated or explicitly described. To be useful the shape change shall be temporary so as to allow the lens to regain it original shape in the eye and preferably the lens is elastically deformed so as to automatically return to its original shape under non-stressed conditions. Conversely, any major permanent deformation is normally equivalent to a damage of the lens. Typically the incision in the eye is a straight cut with a length between 1 and 6 mm, preferably between 2 and 4 mm, which is laterally widened into a more rounded hole and the lens shape after deformation should be adapted for introduction through such an incision, typically with a generally cylindrical outer surface, possibly slightly flattened into a more elliptical form.
The implanter device described herein can be used for most existing deformable intraocular lenses as superficially described in the introduction, either for cataract or for corrective purposes. The lenses generally comprise an optic part and a haptic part. The optic part provides the refractive properties and can have any desired optic property, such as strongly positive refraction for replacement of the natural lens or positive or negative refraction to any degree for corrective purposes. The optic part is generally lens shaped but can have other initial forms, e.g. bag form for after-filling with refractive liquid or mass, other forms for re-shaping or cross-linking within the eye or pre-deformed lenses with memory for recovery of the memorized form in the eye. The optical part edge can be sharp, blunt or flat. The haptic part serves the purpose of contacting the eye inner circumference so as to center and stabilize the optical part in the eye. The haptic may be formed as flat wings extending from the optical parts, similarly shaped loops or, most preferably, two or more flexible legs spiraling around the optical part. Any lens type can be used with the present device as long as it is deformable in the sense of having the ability to have smaller than final dimensions in the eye, the smaller dimensions being suitable for insertion through a small incision in the eye.
The device for folding or deforming soft lenses according to the present invention can be said to include basically a housing, a lens transportation duct for the lens and a plunger arrangement for displacement of the lens in the duct.
The housing shall be understood in broad sense and may take a variety of forms. The device housing represents the point of reference for the lens positions and the movements described, such as its movement from a rear to a front position and its ejection from the device. The minimum functional requirement is that the housing includes or offers a support for the plunger and the lens duct part. In use the duct part is preferably arranged stationary with respect to the housing. The duct containing part can be integral with the housing, e.g. for simplest and cheapest design, or attachable to the housing, e.g. for the common purpose of allowing insertion of a lens receiving cassette with or for deformation of the lens. The plunger arrangement should allow plunger movement with respect to the housing so as to allow at least the plunger front part to perform an axial movement with respect to the duct. As in common practice, however, it is preferred that the housing forms a container at least partly embracing the parts and preferably also to such an extent that only the features designed to be controlled or monitored by the operator are externally exposed, e.g. a plunger actuating control or knob, to give an overall convenient design to use. Also in accordance with common practice the housing may be dividable or openable, e.g. for loading the lens or to facilitate cleaning or sterilization.
Many of the features of the invention give advantages for any type of duct with the minimum requirement that the duct should be adapted for some axial length transport by use of the plunger, e.g. ejection of the lens from a rest position close to a front part release area of the device. Such a minimum movement can suffice for example if the lens is introduced directly into the release area from the front, e.g. by forceps, front pincers, a retractable carrier or paddle or any other tool, or if the lens is pre-loaded into a release area duct part by any external means and attached to the front part of the device as a separate unit or cassette. Generally the narrow part of the device to be introduced through the incision of the eye, hereinafter referred to as the xe2x80x9ctipxe2x80x9d part of the device, is longer than the axial extension of the deformed lens optical part to allow insertion and some manipulation of the lens at the proper depth in the eye, e.g. at least 1.5 and preferably 2 times this length. Among others to keep this tip part of the duct as simple as possible it is preferred to allow for a certain transport duct part for the lens to the rear of the release area. The transport duct and the release area can now take the form of a simple tube with minimum external dimensions adapted to the size of the deformed lens. The tube overall cross-section can be slightly divergent, substantially constant or preferably slightly convergent. The cross-section is preferably round but can have other forms, e.g. slightly elliptical or flattened to conform to an expanded slit incision. The front apex of the tip can be designed to facilitate insertion or to support a gradual rather than abrupt release of the deformed lens, e.g. by having a beveled end cut, axial slits or thinned wall material allowing certain final expansion.
It is possible to introduce the lens in deformed form at the rear end of the tip part of the duct for example by similar means as exemplified for introduction at the tip front. It is preferred, however, that the duct extends into a zone behind the rear end of the tip. Preferably this duct part comprises a deformation chamber zone in which the lens either is introduced in deformed form or becomes deformed. The lens may here be introduced in the device in deformed form e.g. by being inserted in a cassette or chamber unit containing the lens in predeformed state by external means, e.g. in order to keep the implanter device proper as simple as possible. Alternatively the deforming means may be part of the device, e.g. to avoid transitions and necessary handling steps. The lens may be, or have been, deformed by any means. Without being bound by any categorizing principle for deformation methods, some methods can be said to take place by movements or actions lateral to the duct, normally without requiring axial displacement of the lens during the mere deformation step, such as by being squeezed between two hinged or otherwise laterally displaceable half or part pipes, by being forced into a pipe part through an axial or tangential slit, by being similarly pressed between pipe parts hinged in forceps or pliers arrangement or any other manner. After deformation such devices may give a duct of roughly constant cross-section. In contrast some methods require axial displacement of the lens for deformation, such as when the lens is forced through a duct of varying cross-section shape or area over its axial length, roughly corresponding to the desired folding or deformation pattern for the lens. Independent of deformation method or device integration principle used the deformation chamber front duct end cross-section should conform to the connecting duct part, be it the tip part of the duct as described or any intermediate duct part inserted to provide transition or for any secondary objective such as for handling, manufacture or space considerations.
For many purposes the lastmentioned deformation method, involving transport in a duct of varying shape, is to be preferred. This method will be referred to as converging channel method since the duct necessarily has to shrink in at least one dimension lateral to the duct axis, normally along the largest dimension of the un-deformed lens, in order to reshape the lens into a form suitable for implantation, independent of the size of total cross-section area, which may be constant or also shrinking. For purposes of description of the convergent channel said dimension of the channel perpendicular to the duct axis and corresponding to the lens extension from edge to edge shall be referred to as channel xe2x80x9cwidthxe2x80x9d or xe2x80x9clateralxe2x80x9d dimension whereas the dimension perpendicular to the duct axis and corresponding to the lens thickness shall be referred to as channel xe2x80x9cheightxe2x80x9d. The channel inner surface having an overall convex shape shall be referred to as the channel xe2x80x9croofxe2x80x9d whereas the opposing surface having an overall concave shape shall be referred to as the channel xe2x80x9cfloorxe2x80x9d. The converging channel duct type can easily be integrated in an implanter device due to its simplicity, is consistent with a smooth duct, can exploit the piston system also for lens travel through the converging duct part and do not require great skill at lens insertion. Such general advantages of even known convergent channel designs can be exploited together with many aspects of the present invention although prior art constructions have certain disadvantages, especially in respect of haptic accommodation and undue lens deformation or damage under displacement in the duct. Commonly the piston used to push the lens in the converging channel has a front size adapted for the narrowest part of the channel, i.e. at tip exit. A first disadvantage of this design is that the piston front initially attacks the unfolded lens over only a fraction of its lateral extension, transversal to the duct, giving high and possibly destructive point pressures during the early displacement phases. A second disadvantage is that the rear part of the converging channel need to have a larger height extension, transversal to the duct but normal to the optic plane, than required by the thickness of the un-deformed optic part of the lens in order to accomodate the plunger, typically giving a cross-section roof surface with three recesses separated by two ridges. When pushed the deformable lens tends to swell and expand into the enlarged height space and become caught between the plunger and the narrowing walls further down in the duct, resulting in uncontrolled folding, increased friction, damage or even cutting of the lens. The added space is here situated at the worst position possible, namely at the center of the roof against which the lens necessarily is pressed when bent and amplified by its elastic tendency to return to flat form. Similar problems may occur if the at non-closed channel circumference parts, e.g. at slits and cut-outs, through which the lens may swell. Known is also to push with a soft cylinder type plunger front, able to fill out both an initial large channel and a later narrower channel. However, the lens folding initiation is here entirely uncontrolled, as at least the rear channel part is not at all adapted to the size or shape of the lens. Furthermore, the plunger fills out and press against the channel walls, giving no space for the haptic or catching trailing haptic between plunger and wall.
According to one aspect of the present invention the above problems in connection with common converging channel designs are avoided by adapting the duct cross-section, at least over a part of the converging channel length, to the size and shape of the cross-section of the lens optic during folding. When the cross-section through the lens is referred to it shall be understood to be taken at the point of largest area, normally at the center of the optic through the lens thickest part. The said adaptation means that the channel cross-section substantially corresponds to the cross-section of the lens, possibly with minor deviations explained below. It is preferred that the channel circumference is closed. It is also preferred that at least at the height in the middle of the duct, where the thickest part of the lens optic passes, should not be enlarged in its roof part, so to avoid swelling of the deformed lens in this direction, but should substantially correspond to said lens optic thickness. In the channel floor part minor enlargements can be allowed since the lens is not pressed against the floor. Furthermore, the floor has a larger available lateral extension than the roof. If desirable a preferred use of this observation is to locate a guiding groove for the plunger at this position, which in cooperation with a corresponding structure on the plunger may serve the dual purpose of stabilizing the plunger run and restrict its forward travel, e.g. not to be released in or extend too far into the eye, by a suitable termination point for the slit. Still such enlargement should be small and preferably less than 1.5 and more preferably less than 1 mm in the lateral direction whereas its depth is less relevant. Sharp edges on the enlargement is preferred not to facilitate lens expansion therein. Laterally from the central parts of the channel the shape is less demanding, and need not exactly correspond to lens height. Yet the height is preferably reduced in relation to the height at the center. At the far edges the height becomes zero although some extra lateral space is allowed and even may be preferred to give room for haptics, their free and/or their anchoring parts. In particular these design considerations means that the roof of the duct then need not be designed with the abovesaid three recesses and two ridges but may have a line of continuous curvature. Nor should the cross-section be round or elliptical. Expressed in another way the cross-section should have the overall shape of a crescent, at least somewhere along the duct and preferably over the major part between initial bending of the lens and until edge meeting. The shape of the crescent edges are not so critical but can be sharp, blunt or square. The crescent can be symmetrical, e.g. in the form of a xe2x80x9cCxe2x80x9d when creating a folding pattern in which the lens edges meet head on in the later part of the duct to be pressed against each other, suitable for thick lenses, or unsymmetrical, e.g. in the form of a xe2x80x9c6xe2x80x9d for a folding pattern in which the edges meet in an overlapping manner in the later part of the duct to initiate a spiral folding of the lens, suitable for thin lenses. Since the duct cross-section need not have additional area for a plunger the cross-section area can be substantially constant along a major part the convergent duct and most preferably adapted to the major cross-section area of the deformed lens, disregarding here any small convergence dictated by convenient insertion or lens diameter reduction resulting from axial elongation due to radial deformation. The lens may be pushed in the described duct by means of any single or multiple plunger that can be accommodated therein. For reasons outlined it is preferred that the plunger front is larger than the largest circular shape that can be accommodated in the crescent, by being laterally enlarged to cover a larger area on the lens. However, such a shape may jam when the duct shape changes which can be cured by using different plungers for different axial sections of the duct. It is preferred, however, to use a re-shapeable plunger, able to accommodate to the shape variations of the duct, to be further described below.
The plunger of the device basically performs the act of displacing the lens though the duct for which purpose it should be designed to be accommodated in the duct. It could be designed to be accommodated in only a part of the duct, e.g. an initial converging part, and replaced with another plunger for remaining parts of the duct. Preferably the same rod is used throughout the duct for which purpose it should be accommodated all the way up to the tip and possibly somewhat longer for manipulation of the lens in the eye. For this basic purpose any known design can be used, including jaw and paddle type of plunger devices, which contacts and transmit force to the lens at its periphery, i.e. a contact surface substantially parallel with the duct axis. Among others in order to reduce incision size, avoid risks of lens damage when squeezing them in such devices and eye damage when unfolding or releasing such plungers in the eye it is preferred to use xe2x80x9cpushingxe2x80x9d plungers by which shall be understood plungers that contacts and transmit force to the lens at a contact surface substantially transversal to the duct axis. Known pushing plunger types can be used, such as a simple rod with hard or soft front, filling out the duct area. For best control and least risks for damage it is desirable to push the lens by action on its optic part rather than its haptic parts. To this end the plunger front part is often provided with features for avoiding contact with the haptics, which may be different for different haptic types. For wing type haptics the plunger front can be provided with an axial slit deep enough to accommodate the trailing haptic and allow the fork type front to attack the optic of the lens. For looped wings the plunger front alternatively can be designed as a hook or head and neck with the hook or head passing through the loop. Spiralling haptics behave more randomly but most proposals take advantage or their tendency to localize close to the wall by providing some clearance between plunger and wall, e.g. by making the plunger smaller than the duct, by eccentric orientation in the duct, by cut-outs on the plunger front, possibly assisted by a narrower neck behind the front head part, allowing a more free orientation of the haptic here with maintained surface of the head. Alternatively the duct can be broadened to provide space for the haptic or slits can be provided along the duct to allow the haptics to extend out from the duct into the surroundings.
For many aspects of the present invention any of the above described plunger solutions can be used. According to one aspect of the present invention plunger is provided which can be re-shaped between a first form with high lateral to height extension ratio into a second form with less lateral to height extension ratio. This lateral to height ratio will hereinafter be referred to as elongation degree and should preferably in the first form be larger than 1, preferably larger than 1.5 and most preferably larger than 2, or 2.5 or even 3. In the second form the elongation degree should be smaller than in the first form and shall include an elongation degree of 1, i.e. a symmetrical round or polygon of square shape, e.g. to conform to the final duct part for a fully folded or deformed lens. The design preferably allows a change in elongation degree between a first and a second form, expressed as the quotient between the two elongation degrees, of at least 1.5, preferably at least 2, at least 2.5 and most preferably at least 3. These values mainly relates to the front-part of the plunger. Certainly different parts of an elongated plunger may have different elongation degrees, e.g. when extending through a duct of varying shape. Such a plunger has several advantages and utilities. It may for example adapt to and give clearance for different types of haptic and different random positions for the haptic parts. It may adapt to and maintain a distributed pressure surface for changing duct cross-sections for any purpose, such as when pushing a lens into the duct in the first place, at transitions in the duct and well as for conforming in accord with a gradually expanding lens at release. It is particularly useful in connection with converging channel deformation methods, and especially in connection with the above described duct designs containing crescent form cross-sections, where a re-shapeable plunger serve to maintain a large pressure surface without duct enlargements dictated by the plunger as such and one and the same plunger may be used throughout the duct. In order to give these advantages the re-shapeable plunger should be of the pushing type, i.e. providing a front contact surface with the lens running substantially transversal to the duct axis, e.g. having a substantial surface component corresponding to a cross-section through the duct.
The plunger may be given re-shapeable properties by being made in an elastic material. Among others in order to minimize the pressures exerted on the duct walls, e.g. to avoid haptic capture, it is then preferred that the shape of the plunger in un-stressed condition is elongated in the above sense of having an elongation degree larger than 1 and preferably the elongation degrees mentioned above for the first form. Preferably the form roughly corresponds to the duct rear end, in turn roughly corresponding to the unstressed lens, resulting in a folding pattern for the lens similar to that for the lens.
It is preferred that the re-shapeable plunger is made of substantially rigid and form stable material, such as metal or hard plastic, at least in its front part. This will further reduce or eliminate pressure against the duct walls when applying axial pushing forces on the plunger and facilitate implementation of the plunger parts behind the front, which should sustain axial forces, in similar and preferably the same material as the plunger front, e.g. as an integral piece of plastic material. This can be implemented in the form of a multipartplunger wherein the lens is affected by two or more individual parts, which are allowed to rearrange in relation to each other. Preferably the parts are axially extended xe2x80x9cfingersxe2x80x9d able to rearrange, e.g. between a flat configuration with the fingers laterally next-to each other and a rounded configuration for example in the form of a bundle. Such fingers may be entirely separated from each other to allow entirely free rearrangement. They may be pushed at their rear ends individually, e.g. enabling different axial pushing programs for each finger allowing different number of fingers to affect the lens at different sections of the duct, e.g. to adapt to a truly converging duct. Alternatively the fingers are axially moved with a common pusher, e.g. enabling a constant cross-section area to affect the lens throughout the duct length. For the latter purpose it is preferred to join the fingers to have a more controlled rearrangement pattern. The joints can be arranged anywhere along the fingers, e.g. at the rear to allow space between the fingers for reception of haptic or at the front to add some pushing surface from the joints and to guide the haptics towards the duct wall. A preferred joint type is any structure able to act as a hinge, with a hinge axis substantially in the axial direction. Such hinges may be designed as regular hinge constructions but preferably, especially for disposable constructions, as a living hinge in the form of a contact point or skin between the fingers. Preferably the hinge part is given a certain lateral extension to allow the fingers to fold into contact upon each other or almost so if it is desirable to maintain a separation between the fingers, e.g. for the haptics. For best re-shaping ability each finger is preferably joined only to its two neighbors except for the end fingers which are joined to its single neighbor. The number of finger can vary. An abundance of fingers can be used to form a brush type plunger. They can be separate, joined at a rear location allowing the front parts fairly free rearrangement capabilities or in the front, in which case, however, the individual fingers should be joined in layers to maintain the rearrangement freedom, i.e. each finger preferably being joined to two others in layer form. Among others for best control of the folding pattern and haptic accommodation it is often preferred to use a single layer of fingers and preferably as few as possible to fill out the duct in its most flat part, generally at the entrance side at the rear end of the duct. Preferably the number of fingers is no more than 10, preferably no more than five and most preferably three. The number should be at least two and preferably at least three. It is preferred to use an odd number of fingers, especially for symmetrical duct cross-sections, with a central finger and an even number of fingers arranged around the central. The fingers can be similar in size and shape but it is often preferred to make them different. It is for example beneficial to adapt the finger front surfaces to the height of the duct to make them as large as possible with respect to the duct, which most often is highest at the center, although some clearance is preferred. The finger front shapes can have any form, e.g. a shape like a line, a triangle, square, polygon of regular or irregular configuration, The individual finger forms may also be adapted to each other for best. performance when folded into the most compact form, generally at a front section of the duct, e.g. with sides cut straight, for example with 120 degree angles for three fingers, 90 degree angles for four fingers etc., either to meet without separation to maximize the pushing surface or to create a certain fork-like separation e.g. to accommodate a wing type haptic in between. Alternatively the fronts can be made not to fit in a matching pattern, e.g. small circles or with cut-outs so as to leave uncovered cross-section areas between the fingers and between finger and duct wall, for example to allow passage of spiral haptic. Generally it is preferred that the plunger front does not fully fill out the duct cross-section but leaves at least 5% and preferably at least 10% of the area uncovered although the major part of the area should be filled, preferably at least 60% and most preferably at least 70%.
The above considerations apply to the front of the plunger or the individual fingers thereof directly affecting the lens. Behind the front the plunger or finger may be designed more freely, mainly serving the purpose of transmitting the axial pushing force through the duct although these parts should allow rearrangement of the fingers. Immediately behind the front plunger or fingers may be narrower, forming a neck, e.g. to support a free haptic positioning and its final unobstructed release. It may be advantageous to provide spacer extensions to make contact with the channel walls in order to improve stability. Preferably the body of the plunger has a non-rotational symmetry allowing it to cooperate with a hollow keying member of similar configuration to guide and prevent rotation. A roughly flat plunger design may automatically have this property in connection with a convergent channel of crescent type if it has the ability to bend along such a duct.
The plunger can be driven by any known means. It is possible to apply force directly on the plunger part designed to pass through the duct in which case it is possible to design the plunger as a single piece part. In most cases it is preferred to have a separate driving arrangement arranged including a shaft to affect the duct part, for best design freedom and control. The plunger and the driving arrangement will collectively be referred to as the xe2x80x9cplunger systemxe2x80x9d. For reasons outlined lens movement is essentially a two step process wherein the lens in a first step is moved up to a release position close to the device tip, which step generally is performed prior to eye contact, and in a second step the lens is released, which step generally is performed after insertion of the device tip into the eye. The first step in turn may be divided into a lens deformation step when present, e.g. with convergent channel duct types, and a transport step for the deformed lens up the release position. It is preferred that these steps, at least the first and second steps, are reflected in the manner of handling the device, preferably so that at least two different actions are required from the operator, especially in order to avoid inadvertent lens release. The plunger may be driven by motor means to limit operator actions to handling of control means such as a control button. The motor may be an electric motor driving a shaft, possibly via a transmission such as screw and nut spindle arrangement. Pneumatic or hydraulic motors may be used in which case a cylinder and piston arrangement may be needed to apply force to a driving shaft. A mechanical spring system can be used directly or indirectly acting as or on a driving shaft. In motor driven devices the different action requirement can be met by an arrangement needing at least two triggering actions for the first and second step respectively, e.g. by use of two triggers or dual actions on the same trigger. In many instances it is preferred to use purely manual driving of the plunger, e.g. to keep the device simple, lightweight and handy and to allow operator tactile feedback from the steps taken. A shaft for pushing of the plunger can be manually driven by an actuator in any known manner, e.g. by a handle for direct axial movement in a syringe type manner, via a transmission such as a lever, possibly in connection with teeth or friction coupling allowing repeated action, a wheel, possibly a gear wheel, a screw and nut arrangement for rotational advancement or any similar arrangement. The different action requirement can be satisfied, e.g. by an arrangement needing repeated action on the mechanism or preferably by combining at least two different actuation principles. A preferred arrangement of the latter type is a construction in which advancement in the first step takes place by a rotational movement applied to an actuator, transformed into a longitudinal movement via a screw and nut arrangement, serving to give a slow, cautious and controlled initial advancement of the lens, also allowing sufficient force to be applied in case of simultaneous deformation, e.g. in a convergent channel duct type. Further that final advancement in the second step takes place by a substantially axial movement of the actuator, without need for substantial rotation and preferably that rotation during this step is prevented, serving to allow a very simple release movement for the lens preventing rocking or tearing movements in the sensitive eye incision and being consistent with a single hand grip. The latter movement can be implemented by letting the screw and nut parts to go out of engagement at the point where axial movement shall be allowed. Preferably the transition between the first and second steps is guided so as to provide a stop for the rotational movement and only the substantially axial movement thereafter. This can be accomplished by a track having a screw-threaded part continuing in a substantially axial part and cooperating with a follower element, e.g. a point protrusion, able to follow the track. A design of this kind mainly described in connection with a syringe type device is disclosed in U.S. Pat. No. 5,728,075, incorporated herein by reference. The track and follower principle can be generalized to feature any desired movement program, not only the threaded and straight mentioned but also a screw movement with variable pitch, e.g. with a gear ratio adapted to the force requirement in each phase or part of the duct, as described. For tracks of varying curvature preferably only one follower in each track is provided. but several parallel tracks with one follower for each can be provided to increase mechanical stability. For the present purposes the final axial movement is quite short, e.g. less than 30 mm, preferably less than 25 mm and most preferably less than 15 mm, but is generally larger than 5 mm, preferably larger than 8 mm and most preferably larger than 10 mm. In relative terms the length is about the length of the deformed lens, normally axially elongated in relation to its un-stressed dimensions due to radial compression, and preferably longer than this axial length. The axial displacement of the plunger during the first step generally is longer than in the second step. Preferably one of the track or follower is arranged on the housing and the other on the plunger system. Nothing prevents that several parallel or serially arranged tracks with a corresponding number of followers are used and disposed in any manner between housing and plunger system as long as the described movement pattern is obtained. Among others in order to avoid malfunction, interference or damage of the track and follower system it is preferred to arrange these parts so as to be hidden from the device outside. A preferred way for this it to make a housing part and a plunger system part in the form of tubes, preferably with round section, which tube parts overlap in a telescoping manner and to arrange the track and follower between the telescoping surfaces, for best protection most preferably so that the track is arranged on the inner side of one of the tubes and the follower or followers on the outer surface of the other tube. For best accessibility it is preferred to make the plunger system tube part the outermost tube part. Certainly various combinations of the above-described principles can be used.
Various other features can be included in the plunger system and housing to obtain secondary advantages. The housing can have a finger-grip as a counter-support for especially the forward movement of an actuating part of the plunger system. Windows or holes may be arranged on the housing to allow monitoring of the plunger movement. The device of the present invention can be devised as a reusable device for repeated use, in which case the plunger system should allow retraction of the plunger. Due to its simplicity it can also be used as a disposable device for single use, in which case it may be an advantage if it can be moved only in the forward direction, e.g. to prevent re-use, which can be accomplished simply by having an interruption anywhere in the plunger shaft sequence for pushing. As most improper folding of the lens manifests itself in excessive displacement forces needed, the plunger system may also include a force sensitive mechanism, e.g. a pressure sensitive clutch disconnecting at a certain force, e.g. as described in U.S. Pat. No. 5,921,989. Since a single device may be used for different lenses, in respect of type or refraction degree, the proper force may vary and for reasons outlined the proper force requirements may also vary along the duct, especially for convergent channel duct types. Hence it is preferred with a system that signal to the operator when a certain pressure is exceeded or more preferably, signal the actual force to the operator in order to permit monitoring of a proper force profile for each implant situation. Such a signal system can be implemented in electronic form, e.g. with a transducer, or in mechanical form, e.g. with a torsion-metering device.
The device may be equipped with a lens receiving chamber for the un-stressed or only slightly stressed lens in a position suited to be abutted and pushed by the plunger. This is of particular interest in connection with the convergent channel type deformation method in which the plunger is used as a major means for lens deformation. As said the unfolded lens is susceptible to rotation and misalignment due to its large lateral extension as well as its far extending haptics and it is preferred to localize and stabilize the lens properly before folding initiation. This can be done by action on the lens optic part, e.g. by applying pressure substantailly transversal, i.e. perpendicular, to the lens plane e.g. by squeezing it between roof and floor of the receiving chamber for example when closing a door to the chamber or between members, e.g. bars or rails continuing into the duct proper, between which members the lens is inserted. Preferably then the lens is initially slightly bent along a fold axis parallel to the duct axis since any rotation then a lens rotation will be counteracted by the necessary change in deformation resulting from the change in fold line. For better control and leverage against rotation it is preferred to stabilize the lens haptics. This can be done by placing pressure transversal to the lens plane in a similar manner as described for the lens optic but it is preferred to arrange delimiting structures running in the transversal direction so as to stop lens rotation through abutment between haptic and the structure which can be used for all haptic types. Preferably at least two structures are used and most preferably arranged to prevent rotation on opposite directions, e.g. by holding one haptic on its both sides or by holding one haptic against rotation in one direction and a second haptic against rotation in the other direction. Most preferably two structures are used at each haptic, e.g. four structures for two haptics, two around both haptics, and arranged to counteract rotation in both directions at each haptic. For best stability the structures are preferably present close to the connection between haptic and optic. In addition the structures may be present all or the major part of the haptic periphery, e.g. to fully define their position, but it is often sufficient with point contact, e.g. from pins running transversely to the lens plane, at the described locations and a small size is also preferred for facilitated disablement of the structures before lens displacement, in which connection the structures and lens should be moved in relation to each other to such an extent as to free the haptics for forward movement. The lens can be made to move away from the structures, e.g. by being placed on a carrier, which is moved with at least a movement component in the transversal direction but preferably also with a movement component in the axial direction in or into the duct. Among others to have a simpler device it is preferred to arrange the structures movable or removable in relation to the housing, e.g. by being separate or resilient structures that can be displaced or deflected, either manually for example by being accessible from the outside the chamber for example by being attached to a removable common plate or automatically by means inside the device for example by being pushed away by a part of the plunger system for example by corresponding ramped surfaces. Another preferred arrangement is to allow for deflection of the structures by and when a door to the chamber is closed. The structures may fix the lens somewhat different depending on type. Lenses with wing type haptics preferably are placed with the wings axially, i.e. with one wing extending forwards and the other rearwards, whereas lenses with spiral haptics preferably are positioned with the diameter line between two haptic anchoring points forming an angle somewhere between axial and right angle thereto, say about 45 degrees with respect to the axis, and with the forward pointing leg anchoring point in front of the anchoring point for the rearward pointing leg, all to avoid that any part of the haptics collide during folding.
The lens receiving chamber can have any other feature improving its functional and convenient properties. Preferably the seat for the lens is roughly shaped corresponding to the lens shape although it may have cutouts to accommodate the arms of forceps when placing the lens in the chamber. The chamber is preferably designed to allow opening and closing, e.g. by being made of two parts that can be releasable connected, preferably including a hinge for convenient operation, e.g. around a transversal axis but preferably for easiest access around an axis substantially parallel to the duct axis. A lock can be provided, either releasable or permanent to avoid reuse of disposable devices. Generally a convergent channel type duct cannot without difficulty be manufactured in one piece and it is preferred to make it in two pieces. The division should be made so as to limit the risk for overshooting joint surfaces, e.g. to avoid lens cutting, for connection gaps, e.g. to avoid lens creeping, and for divisions in the area of haptics, e.g. to avoid nipping. For the crescent duct type described it is preferred to position the innermost division line axially along the crescent lateral terminations to meet at the front roof end in the area where the crescent ends meet to form a V-shaped floor piece with the apex about where the deformation duct part ends and continues in a transport duct part with roughly constant cross-section profile. With preference the widening part of the V continues over the lens receiving chamber when present and the line may close and terminate safely behind the lens. Most preferably the now described roof piece acts as an openable part of the device for accessing the duct and the lens receiving chamber as described. It is also preferred that the contact surface between the parts in the joint run perpendicular, or with a component perpendicular, to the lens plane at the inner part of the division line closest to the lens. This in order to reduce nip risks as compared to joint surfaces arranged in the lens plane.
The device can be manufactured in any material compatible with the lenses and able to sustain the forces involved such as glass, metal and preferably plastics. Suitable plastics are polyethylene, polypropylene, polycarbonate, polyamid, polymethylmethacrylate, PET, PBT, PEI, PES, PPO, POM, GPPS etc. It is preferred to select a transparent material for the duct containing part to allow the operator monitoring lens and plunger progression. The preferred manufacturing method is injection molding. At least the duct surfaces can be coated or chemically modified to reduce friction against the lens, e.g. glycerin, silicone, polytetrafluoroethylene or hydrophilic coatings of polymers or hydrogels. An eye surgically acceptable lubricant can also be used on the lens or in the duct, e.g. Healon(copyright).
How to use the device has been described above in connection with each feature. Before the surgical situation the device can be prepared in various ways. The lens can be preloaded into the device and sterilized at a manufacturing site for storage and stored and transported within the device, which may be of particular interest in connection with disposable devices. A door over the loading chamber can be only partially closed during transport and storage and the lens held in place by the structures described after which the door is fully closed to displace the structures and free the lens. Alternatively the lens may be charged into the device in connection with use which may be of interest for reusable devices and if the lens is charged into the device in deformed condition by any of such methods enumerated in order to avoid gradual permanent deformation. The lens may be introduced in cassette form, e.g. to allow adaptation between cassette and lens for different types and diopters or for permitting any external tools for deformation. The cassette may comprise any part or parts between the lens receiving chamber and the tip. The lens may also be introduced in naked form, e.g. when the device comprises the deformation means.